Fix panics when m-mapping head chunks (#10316)

* Fix panics when m-mapping head chunks

Signed-off-by: Ganesh Vernekar <ganeshvern@gmail.com>

* Fix review comments

Signed-off-by: Ganesh Vernekar <ganeshvern@gmail.com>

* Fix reviews

Signed-off-by: Ganesh Vernekar <ganeshvern@gmail.com>

tsdb/chunks/head_chunks.go

@@ -137,9 +137,8 @@ func (f *chunkPos) cutFileOnNextChunk() {
 	f.cutFile = true
 }
 
-// initSeq sets the sequence number of the head chunk file.
-// Should only be used for initialization, after that the sequence number will be managed by chunkPos.
-func (f *chunkPos) initSeq(seq uint64) {
+// setSeq sets the sequence number of the head chunk file.
+func (f *chunkPos) setSeq(seq uint64) {
 	f.seq = seq
 }
 
@@ -181,7 +180,7 @@ type ChunkDiskMapper struct {
 	writeBufferSize int
 
 	curFile         *os.File      // File being written to.
-	curFileSequence int           // Index of current open file being appended to.
+	curFileSequence int           // Index of current open file being appended to. 0 if no file is active.
 	curFileOffset   atomic.Uint64 // Bytes written in current open file.
 	curFileMaxt     int64         // Used for the size retention.
 
@@ -321,7 +320,7 @@ func (cdm *ChunkDiskMapper) openMMapFiles() (returnErr error) {
 		}
 	}
 
-	cdm.evtlPos.initSeq(uint64(lastSeq))
+	cdm.evtlPos.setSeq(uint64(lastSeq))
 
 	return nil
 }
@@ -869,16 +868,33 @@ func (cdm *ChunkDiskMapper) Truncate(mint int64) error {
 		// won't do any harm.
 		cdm.CutNewFile()
 	}
-	errs.Add(cdm.deleteFiles(removedFiles))
+	pendingDeletes, err := cdm.deleteFiles(removedFiles)
+	errs.Add(err)
+
+	if len(chkFileIndices) == len(removedFiles) {
+		// All files were deleted. Reset the current sequence.
+		cdm.evtlPosMtx.Lock()
+		if err == nil {
+			cdm.evtlPos.setSeq(0)
+		} else {
+			// In case of error, set it to the last file number on the disk that was not deleted.
+			cdm.evtlPos.setSeq(uint64(pendingDeletes[len(pendingDeletes)-1]))
+		}
+		cdm.evtlPosMtx.Unlock()
+	}
+
 	return errs.Err()
 }
 
-func (cdm *ChunkDiskMapper) deleteFiles(removedFiles []int) error {
+// deleteFiles deletes the given file sequences in order of the sequence.
+// In case of an error, it returns the sorted file sequences that were not deleted from the _disk_.
+func (cdm *ChunkDiskMapper) deleteFiles(removedFiles []int) ([]int, error) {
+	sort.Ints(removedFiles) // To delete them in order.
 	cdm.readPathMtx.Lock()
 	for _, seq := range removedFiles {
 		if err := cdm.closers[seq].Close(); err != nil {
 			cdm.readPathMtx.Unlock()
-			return err
+			return removedFiles, err
 		}
 		delete(cdm.mmappedChunkFiles, seq)
 		delete(cdm.closers, seq)
@@ -886,13 +902,13 @@ func (cdm *ChunkDiskMapper) deleteFiles(removedFiles []int) error {
 	cdm.readPathMtx.Unlock()
 
 	// We actually delete the files separately to not block the readPathMtx for long.
-	for _, seq := range removedFiles {
+	for i, seq := range removedFiles {
 		if err := os.Remove(segmentFile(cdm.dir.Name(), seq)); err != nil {
-			return err
+			return removedFiles[i:], err
 		}
 	}
 
-	return nil
+	return nil, nil
 }
 
 // DeleteCorrupted deletes all the head chunk files after the one which had the corruption
@@ -907,14 +923,27 @@ func (cdm *ChunkDiskMapper) DeleteCorrupted(originalErr error) error {
 	// Delete all the head chunk files following the corrupt head chunk file.
 	segs := []int{}
 	cdm.readPathMtx.RLock()
+	lastSeq := 0
 	for seg := range cdm.mmappedChunkFiles {
 		if seg >= cerr.FileIndex {
 			segs = append(segs, seg)
+		} else if seg > lastSeq {
+			lastSeq = seg
 		}
 	}
 	cdm.readPathMtx.RUnlock()
 
-	return cdm.deleteFiles(segs)
+	pendingDeletes, err := cdm.deleteFiles(segs)
+	cdm.evtlPosMtx.Lock()
+	if err == nil {
+		cdm.evtlPos.setSeq(uint64(lastSeq))
+	} else {
+		// In case of error, set it to the last file number on the disk that was not deleted.
+		cdm.evtlPos.setSeq(uint64(pendingDeletes[len(pendingDeletes)-1]))
+	}
+	cdm.evtlPosMtx.Unlock()
+
+	return err
 }
 
 // Size returns the size of the chunk files.

tsdb/db_test.go

@@ -3512,3 +3512,61 @@ func newTestDB(t *testing.T) *DB {
 	})
 	return db
 }
+
+// Tests https://github.com/prometheus/prometheus/issues/10291#issuecomment-1044373110.
+func TestDBPanicOnMmappingHeadChunk(t *testing.T) {
+	dir := t.TempDir()
+
+	db, err := Open(dir, nil, nil, DefaultOptions(), nil)
+	require.NoError(t, err)
+	db.DisableCompactions()
+
+	// Choosing scrape interval of 45s to have chunk larger than 1h.
+	itvl := int64(45 * time.Second / time.Millisecond)
+
+	lastTs := int64(0)
+	addSamples := func(numSamples int) {
+		app := db.Appender(context.Background())
+		var ref storage.SeriesRef
+		lbls := labels.FromStrings("__name__", "testing", "foo", "bar")
+		for i := 0; i < numSamples; i++ {
+			ref, err = app.Append(ref, lbls, lastTs, float64(lastTs))
+			require.NoError(t, err)
+			lastTs += itvl
+			if i%10 == 0 {
+				require.NoError(t, app.Commit())
+				app = db.Appender(context.Background())
+			}
+		}
+		require.NoError(t, app.Commit())
+	}
+
+	// Ingest samples upto 2h50m to make the head "about to compact".
+	numSamples := int(170*time.Minute/time.Millisecond) / int(itvl)
+	addSamples(numSamples)
+
+	require.Len(t, db.Blocks(), 0)
+	require.NoError(t, db.Compact())
+	require.Len(t, db.Blocks(), 0)
+
+	// Restarting.
+	require.NoError(t, db.Close())
+
+	db, err = Open(dir, nil, nil, DefaultOptions(), nil)
+	require.NoError(t, err)
+	db.DisableCompactions()
+
+	// Ingest samples upto 20m more to make the head compact.
+	numSamples = int(20*time.Minute/time.Millisecond) / int(itvl)
+	addSamples(numSamples)
+
+	require.Len(t, db.Blocks(), 0)
+	require.NoError(t, db.Compact())
+	require.Len(t, db.Blocks(), 1)
+
+	// More samples to m-map and panic.
+	numSamples = int(120*time.Minute/time.Millisecond) / int(itvl)
+	addSamples(numSamples)
+
+	require.NoError(t, db.Close())
+}

tsdb/head.go

@@ -627,7 +627,8 @@ func (h *Head) loadMmappedChunks(refSeries map[chunks.HeadSeriesRef]*memSeries)
 		if !ok {
 			slice := mmappedChunks[seriesRef]
 			if len(slice) > 0 && slice[len(slice)-1].maxTime >= mint {
-				return errors.Errorf("out of sequence m-mapped chunk for series ref %d", seriesRef)
+				return errors.Errorf("out of sequence m-mapped chunk for series ref %d, last chunk: [%d, %d], new: [%d, %d]",
+					seriesRef, slice[len(slice)-1].minTime, slice[len(slice)-1].maxTime, mint, maxt)
 			}
 
 			slice = append(slice, &mmappedChunk{
@@ -641,7 +642,9 @@ func (h *Head) loadMmappedChunks(refSeries map[chunks.HeadSeriesRef]*memSeries)
 		}
 
 		if len(ms.mmappedChunks) > 0 && ms.mmappedChunks[len(ms.mmappedChunks)-1].maxTime >= mint {
-			return errors.Errorf("out of sequence m-mapped chunk for series ref %d", seriesRef)
+			return errors.Errorf("out of sequence m-mapped chunk for series ref %d, last chunk: [%d, %d], new: [%d, %d]",
+				seriesRef, ms.mmappedChunks[len(ms.mmappedChunks)-1].minTime, ms.mmappedChunks[len(ms.mmappedChunks)-1].maxTime,
+				mint, maxt)
 		}
 
 		h.metrics.chunks.Inc()
@@ -673,7 +676,10 @@ func (h *Head) removeCorruptedMmappedChunks(err error, refSeries map[chunks.Head
 	level.Info(h.logger).Log("msg", "Deleting mmapped chunk files")
 
 	if err := h.chunkDiskMapper.DeleteCorrupted(err); err != nil {
-		level.Info(h.logger).Log("msg", "Deletion of mmap chunk files failed, discarding chunk files completely", "err", err)
+		level.Info(h.logger).Log("msg", "Deletion of corrupted mmap chunk files failed, discarding chunk files completely", "err", err)
+		if err := h.chunkDiskMapper.Truncate(math.MaxInt64); err != nil {
+			level.Error(h.logger).Log("msg", "Deletion of all mmap chunk files failed", "err", err)
+		}
 		return map[chunks.HeadSeriesRef][]*mmappedChunk{}
 	}
 
@@ -681,6 +687,9 @@ func (h *Head) removeCorruptedMmappedChunks(err error, refSeries map[chunks.Head
 	mmappedChunks, err := h.loadMmappedChunks(refSeries)
 	if err != nil {
 		level.Error(h.logger).Log("msg", "Loading on-disk chunks failed, discarding chunk files completely", "err", err)
+		if err := h.chunkDiskMapper.Truncate(math.MaxInt64); err != nil {
+			level.Error(h.logger).Log("msg", "Deletion of all mmap chunk files failed after failed loading", "err", err)
+		}
 		mmappedChunks = map[chunks.HeadSeriesRef][]*mmappedChunk{}
 	}
 

tsdb/head_test.go

@@ -3143,3 +3143,58 @@ func TestChunkSnapshotTakenAfterIncompleteSnapshot(t *testing.T) {
 	require.Equal(t, 0, idx)
 	require.Greater(t, offset, 0)
 }
+
+// Tests https://github.com/prometheus/prometheus/issues/10277.
+func TestMmapPanicAfterMmapReplayCorruption(t *testing.T) {
+	dir := t.TempDir()
+	wlog, err := wal.NewSize(nil, nil, filepath.Join(dir, "wal"), 32768, false)
+	require.NoError(t, err)
+
+	opts := DefaultHeadOptions()
+	opts.ChunkRange = DefaultBlockDuration
+	opts.ChunkDirRoot = dir
+	opts.EnableExemplarStorage = true
+	opts.MaxExemplars.Store(config.DefaultExemplarsConfig.MaxExemplars)
+
+	h, err := NewHead(nil, nil, wlog, opts, nil)
+	require.NoError(t, err)
+	require.NoError(t, h.Init(0))
+
+	lastTs := int64(0)
+	var ref storage.SeriesRef
+	lbls := labels.FromStrings("__name__", "testing", "foo", "bar")
+	addChunks := func() {
+		interval := DefaultBlockDuration / (4 * 120)
+		app := h.Appender(context.Background())
+		for i := 0; i < 250; i++ {
+			ref, err = app.Append(ref, lbls, lastTs, float64(lastTs))
+			lastTs += interval
+			if i%10 == 0 {
+				require.NoError(t, app.Commit())
+				app = h.Appender(context.Background())
+			}
+		}
+		require.NoError(t, app.Commit())
+	}
+
+	addChunks()
+
+	require.NoError(t, h.Close())
+	wlog, err = wal.NewSize(nil, nil, filepath.Join(dir, "wal"), 32768, false)
+	require.NoError(t, err)
+
+	mmapFilePath := filepath.Join(dir, "chunks_head", "000001")
+	f, err := os.OpenFile(mmapFilePath, os.O_WRONLY, 0o666)
+	require.NoError(t, err)
+	_, err = f.WriteAt([]byte{1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11}, 17)
+	require.NoError(t, err)
+	require.NoError(t, f.Close())
+
+	h, err = NewHead(nil, nil, wlog, opts, nil)
+	require.NoError(t, err)
+	require.NoError(t, h.Init(0))
+
+	addChunks()
+
+	require.NoError(t, h.Close())
+}